It was to be the rousing finale of their musical show at the June 20 commencement. The kids, dressed up for their big day, would wave tiny American flags — which, as the lyrics proclaim, “still stand for freedom.”

But Hawkins marched in on a recent rehearsal and ordered a CD playing the anthem to be shut off, staffers said.

She told the teachers to drop the song from the program.

“We don’t want to offend other cultures,” they quoted her as explaining.

The curt edict stunned both staff and parents.

“A lot of people fought to move to America to live freely, so that song should be sung with a whole lot of pride,” said mom Luz Lozada, whose son, Daniel, is in kindergarten.

The song has been sung at previous school events. Last year’s fifth-graders, including another Lozada child, performed it at graduation.

“Everybody applauded and whistled,” the mom said. “They gave it a standing ovation.”

A teacher agreed: “It makes them a little goosebumpy and teary-eyed. I’ve never come across anyone who felt it insulted their culture.”

Department of Education spokeswoman Jessica Scaperotti gave The Post an explanation staffers said they never heard — that Hawkins found the lyrics “too grown up” for 5-year-olds.

The song starts: “If tomorrow all the things were gone, I’d worked for all my life. And I had to start again, with just my children and my wife, I’d thank my lucky stars, to be livin’ here today.”

Scaperotti said the department supports the principal’s decision. “The lyrics are not age-appropriate,” she said.

But Justin Bieber’s flirty song about teen romance, “Baby,” was deemed a fine selection for the show. Hawkins had no problem with 5-year-olds singing lines such as, “Are we an item? Girl, quit playing.”

The other songs: “We’re All Together Again,” popular at Scout campfires; “The World is a Rainbow,” which celebrates diversity; “Shake Your Sillies Out” by Raffi; and “You’ve Got a Friend in Me” from “Toy Story.”

Scaperotti noted PS 90 kids recite the Pledge of Allegiance and sing “America the Beautiful” each morning. Insiders say Hawkins tried to end that tradition a couple years ago but staff objected.

The principal, a Jehovah’s Witness, does not recite the pledge because her religion forbids followers to salute any nation’s flag. Staffers gripe she doesn’t stand in respect during the school-wide ritual.

The song uproar comes amid tensions. Hawkins has been called a tyrant and bully by some staffers.

The DOE reprimanded her in 2010 after teachers complained she called the school “racist” and declared: “I’m black. Your previous principal was white and Jewish. More of us are coming.”

Scaperotti said Hawkins is being targeted by the teachers union and has received hate mail, which is under investigation by the NYPD.